1. Field of the Invention
The present invention relates to a segment adapted for use for a rehabilitating pipe that is assembled to rehabilitate an existing pipe, such as a sewer pipe.
2. Description of the Prior Art
A method of rehabilitating an existing pipe is known from Japanese Patent Laid Open Publication No. 2003-286742 and the like, wherein a compound pipe is constructed to rehabilitate an existing pipe, such as a sewer pipe, as shown in FlG. 5, by assembling and laying inside an existing pipe 4 a rehabilitating pipe 3 whose outer diameter is slightly less than the inner diameter of the existing pipe, and then filling and hardening a filler in the gap between the outer circumference of the rehabilitating pipe 3 and the inner wall surface of the existing pipe 4. If the rehabilitating pipe 3 is a circular pipe whose diameter is approximately 1,000-1,800 mm, the rehabilitating pipe 3 is assembled by forming short rings by coupling a plurality of segments 1 in the circumferential direction of the rehabilitating pipe 3, and then successively and mutually coupling the rings in the longitudinal direction of the rehabilitating pipe 3 (ring assembly). Since ring assembly is problematic for the case wherein the rehabilitating pipe 3 has a large diameter of approximately 2,000 mm or greater or is a rectangular pipe, the rehabilitating pipe 3 is assembled by successively coupling the segments 1 in units, one by one, in the circumferential direction and the longitudinal direction of the rehabilitating pipe 3 (unit assembly).
In the construction work of laying the rehabilitating pipe, it is common to position the rehabilitating pipe so that the outer circumference of a lower end part thereof contacts the bottom of the existing pipe. Consequently, particularly in the case of ring assembly, a segment 1′ is moved, as shown in FIG. 7, so that the outer circumference of the lower end part thereof rubs against the pipe bottom 4a of the existing pipe when it is coupled in the longitudinal direction to a segment 1 that is already coupled to the rehabilitating pipe and lies in contact with a pipe bottom 4a. 
The segments 1 and 1′ are usually provided with side plates 102 and 103 on both sides in the longitudinal direction, whose outer surface forms a coupling surface and whose outer entire surface is formed planarly. Consequently, as shown in FIG. 7, it is often the case that waste, sand, and the like get caught on the pipe bottom 4a of the existing pipe between the outer surfaces of the mutual side plates 102 and 103 of the segments 1 and 1′, thereby creating a gap and making it impossible to mutually tightly seal the outer surfaces of the side plates 102 and 103. In such a case, the waste that has gotten caught must be eliminated, which is unfortunately time consuming, and increases the time it takes to perform the coupling work. This problem is remarkable particularly in the case of ring assembly. In addition, if coupling is performed as is without eliminating the waste that has gotten caught, then the above mentioned outer surfaces will not be mutually tightly sealed, creating the problem wherein the watertightness in the coupling portion in the longitudinal direction can no longer be ensured.
It is therefore an object of the present invention to provide a segment for a rehabilitating pipe enabling the coupling work in the longitudinal direction to be performed more simply and in a shorter period of time and enabling the watertightness of the coupling portion in the longitudinal direction to be improved.